The Concept of Normality
by SaintInfernalNeos
Summary: Normality. One's own perception of how the natural order of things should be. But...what happens when that perception is totally screwed up? For a normal human boy raised with a Half-Succubus as 'sister' by their mischievously cunning Succubus mother, it most certainly is. Doesn't help he seems to be like a magnet for everything supernatural, but hey, if he doesn't find it weird...


Hey everyone, happy April Fools! I decided to not break tradition and I ended up doing something crazy and small anyway for today XP! Don't expect it to have a continuation, I'm quite busy with my 3 main fics, but I hope you at least get a good laugh out of this 'prologue' :3

**Disclaimer:** SAO and its characters aren't my property, they're Kawahara Reki's. If they were mine...well, 90% of the current fandom would probably be raging a lot XD

* * *

**Prologue: 'Normal' Boy in Abnormal Household**

Once upon a time (Insert Cliché Reference here), there were two sisters called Midori and Aoi. They were like any other pairs of sisters you could see anywhere in the world…except for a small detail.

They were demons, you see. Succubae, to be precise.

Well, again, that wasn't 100% correct. Midori, after all, was a pure demon, while Aoi was only half-succubus. Their mother had fled to the human world after being fed up with her husband's idiocy while she was pregnant of Midori, and fallen in love with a Japanese man, as she had settled in that land (And was also the reason for the young succubus' oriental name). Aoi had later been born from her relationship with her new love.

Even so, despite not sharing the same biological father, both sisters were inseparable and loved each other very much. Raised half on the traditions of their ancestors from each side of their family, the demonic and the human one, though, it was soon clear how the older sister preferred doing things the Succubus way while the younger was enamored with the human lifestyle.

Despite this, none of them criticized the other's way of living, and their love and respect never waned even one bit. When both met men they were interested in, accepted them for who they were and fell in love (And could keep up with their 'urges' too), there was nothing but blessings from their parents and the other sister.

Kirigaya Minetaka and Narusaka Yukito weren't sure if they were the luckiest men in the world, but they sure felt like it. Sleeping with sex demons, especially if you were married to one, could be terribly draining, but the act was worth every second of utter exhaustion later.

Both couples were happy and, eventually, both conceived children, Midori with just six months of difference under her little sister, probably out of some sense of competitiveness. That said, little Kazuto and little Suguha were born into the world with lots of love and over-exaggerated celebration of their grandparents.

Curiously enough, the boy was born purely human…or, at least, he had so little demon blood on him that no demonic power was felt at all in his body by his mother, aunt or grandmother. Suguha, on the other hand, thrived with the clear evidence that she had been born a perfectly healthy half-succubus. There was rejoicing equally in either side for this, though, as Midori clearly preferred raising her daughter as one of their race while Aoi intended to give Kazuto a happy human life.

Except that…sometimes, Fate can be cruel, and derail plans in the most tragic and/or peculiar ways.

Aoi and Yukito died a year after their son was born, under unknown circumstances. They were making a trip to visit the half-succubus' parents, after having left their son with his aunt's family, only for their car to suffer a malfunction that cost them their lives.

_Everyone_ was perplexed and more than a bit wary about this, given that, unless Aoi had been extremely distracted, there was no way at least she would have died in such a simple thing as a car accident, given her nature. However, nothing else happened, no signals of doom or anyone coming after the rest of the stranded family ever showed up.

Still, even after they relaxed and reluctantly accepting the tragedy may have been only a terrible design of Fate, this still left quite a conundrum.

Little Kazuto was an orphan now. Of course, Midori didn't hesitate in adopting him at all, but that still left her with the dilemma of how to raise her new 'son': Did she follow the same plan she originally had for Suguha? Or did she honor her late sister's wish to give the boy a 'human' life?

Finally, though, and after a few talks with her husband…the woman came to a 'brilliant' solution, one that she was sure would benefit both of her 'children' and ensure they would live a long and happy life, while also still kind of-respecting her dear sister's hopes for her son. Minetaka wasn't as sure if it was the best of ideas, but given that he was soon going to accept a job overseas to ensure they had enough money to keep their now bigger family happy, it wasn't as if he could oppose to it that much.

Besides, how bad it could it be?

* * *

**June 14th, 2014. Kawagoe, Saitama. Kirigaya Household, 09:30…**

Yawning, 5 years old Kirigaya Suguha woke up that day hugged to her beloved big brother, like always. Mumbling in his sleep, the boy hugging his little sister back, Kazuto seemed to almost subconsciously seek out her embrace, which she happily returned, almost tempted to just keep sleeping there instead of waking up for breakfast, despite knowing how much their mom would scold them if she did so.

However, a 'strange' itchy feeling on her back made her blink fully awake and frown, confused. Trying to look over her shoulder wasn't very successful, but at least let her see there seemed to be nothing on the bed digging into her back. However, the weird feeling remained, and it seemed to be coming from something directly on her skin.

"Onii-chan…Onii-chan, wake up!"

"Mugyu…five more minutes, Sugu…"

"I would love to, but there is something weird…my back is itchy."

"Huh? How is that weird?" questioned the little boy while finally opening his eyes, worry filling them upon seeing his little sister's fidgeting expression.

"It's…I think there is something stuck on my back, I don't know. Could you check it for me?"

"Oh…sure?"

A minute later had the siblings sitting on the bed while the frowning Kazuto touched Suguha's upper back, feeling some weird 'nubs' under her pajamas. Asking for his sister to take off her shirt, she hesitantly did so…making the boy gasp in surprise at what he saw.

There, just at the edge of her scapula, two weird black protuberances had appeared, and they even seemed to be wiggling slightly at the same time the little girl fidgeted.

"S-so…what is it, Onii-chan?"

"Uhm…I…I think your back is…growing extra arms?"

"…Onii-chan, you meanie! That's not funny!"

"N-no, I'm not joking! See?" as he said those words, the kid reached out and touched the left nub with his pinky finger, making it wiggle and Suguha to gasp in surprise. "Di-did you feel that…?"

"I…what…?" clearly looking scared now, with even tears feeling her eyes, the little girl broke out crying, making her big brother panic. "Waaaaah! I don't want to grow more arms!"

"A-ah, let's go see mom! She will know what to do!" quickly jumping off the bad, Kazuto half-dragged/half-carried his sobbing sister downstairs, when they found their mother whistling away as she cooked breakfast in an apron…and only an apron.

There was nothing weird with that view in the children's eyes, though, as it was something they had grown up with every day, so the worried boy didn't even slow down while the woman blinked and turned upon hearing her daughter's cries.

"Kazuto, what's wrong with your sister?"

"Mom, Sugu is growing extra-arms from her back!" 'explained' the panicking boy while Suguha just cried harder at the 'reminder'. "What do we do?!"

"…Sugu, dear, let me see your back." speaking with a soft tone, Midori calmed her daughter down and turned her around to look at the small nubs in her back, only to smile and chuckle upon the sight, confusing her children. "Ufufu…it's okay, Suguha, you're not growing extra-arms. Those are just your wings finally developing."

"…wings?" spoke both kids at once with perplexed looks.

"Yes. Like these." casually, as if was the most natural thing in the world, two imposing bat-like wings emerged from the woman's back at the same time two steel-colored horns grew forward from the back of her head, covering her sides and leaving her children speechless and wide-eyed. "See?"

"…mom, you have wings!"

"Heheh, yes dear, I do." laughed Midori while a spade-tipped black tail swayed from her behind, moving like a hypnotic snake for the awed children for a moment as their mother leaned forward, smiling. "I guess it's about time I tell you about your true nature, Suguha."

The next hour was quite shocking for the two siblings. Knowing their mother was a 'demon' would have scared most children, but these two had been raised in a very peculiar way, in which any association of 'devils' and 'evil' had always been omitted or discouraged, and even that from the outside world had always affected them very little, so it generated more awe and excitement than any negative feelings. Plus, it was their mother, who had lovingly raised them as far as they had memory, so that meant it couldn't be anything bad at all, right?

Of course, they were still too young to properly understand what being a 'succubus' entailed, but the gist they got was that Suguha would grow the same wings, horns, and tail that Midori had. The woman also promised she would teach her simple ways to 'hide' her inhuman traits so that she could continue going with her school life like any normal child.

Kazuto seemed much more excited at the idea of having 'powers' that came with their heritage, which was no surprise, given how much of a fan of fictional stories and fantastical TV series the boy was. Eager, he waited for his turn to 'get cool demon powers' to come…except it didn't.

As the months passed and his little sisters grew small horns, a cute tail and her 'back-nubs' became tiny but strong-looking bat-like wings, Kazuto started coming to the realization that he stayed as normal and boring and he has always been. And that didn't sit well with him at all.

By the time a year had passed since the 'reveal' and Suguha was starting, if slowly, to learn how to fly, the boy's childish jealousy had reached its peak, and Midori was extremely worried this would put a grave 'rift' to her 'plans' for her children's future. She was actually debating if explaining the truth about his origins would make her 'son' feel better or worse at that point…

That is, until one day the siblings were alone at home, with Kazuto sitting on the veranda outside the old dojo (Which barely had seen any use since their grandfather from their father's side had passed away) while reading a digital book in his tablet, looking quite bored. Standing not far away, his serious-looking little sister, clad only in her underwear and with all her succubus traits out in the open, was doing her best to flap her wings and lift off the ground.

"Hnngh…! A-ah, look, Onii-chan! I'm doing it!" celebrated Suguha as she started hovering off the ground and flying slowly above their backyard's pond. "I'm flying!"

"Good for you, Sugu, but remember to be careful. Mom may have some special charms around the house so that the neighbors don't see you practice, but you're not supposed to do it when she isn't around." uncaringly replied the little boy while trying to hide his jealousy, not even lifting his eyes from his tablet.

"Moou…! Onii-chan, you're not even looking! Why are you such a meanie with me late…?! UAH!"

_SPLASH!_

Eyes snapping upwards at the scream and the sound of splashing water, Kazuto watched in shock how there were several ripples on the pond and some droplets were still flying through the air as if in slow motion, signaling how his little sister had just fallen in.

His body reacting faster than his conscious mind, the little boy threw his tablet away and rushed to the water, jumping inside and zeroing on Suguha's sinking form, the little girl's wings actually making it harder for her to swim as she hopelessly tried to float upwards, her eyes starting to close while her big brother's hand reached out towards her.

Less than a minute later, Kazuto had his little sister's unconscious form lying beside the point, naked fear in his eyes as he ignored how cold or drenched he was in favor of putting hours of watching movies and some anime to use and tried to give her CPR, hoping to save her life.

Sadly, there was no realistic way for the 6-years-old to accurately realize a cardiopulmonary resuscitation using just media-based knowledge, so all that he managed was to haphazardly press her chest a few times and then clumsily kiss her.

However, the moment he did that, the little boy felt a strange sensation, as if something was being drained from him and into his little sister. He had no time to ponder about that, though, because Suguha started coughing and sputtering the next second, all the water being expelled from her lungs as she shook, looked up at him and hugged him with all her might, breaking down crying right away. Hugging her back, Kazuto started to cry too, and that would be how their mother would find them later, sobbing and holding each other as if they never wanted to let go.

That day, Kirigaya Kazuto realized how foolish he had been, and that it didn't matter if his sister was 'cooler' than him. She was still his precious Sugu, the person he was the closest to in the whole world.

So, what if he didn't have any amazing demon powers? He was still her big brother! And, as that incident had proved, she still needed him to protect her! Determined to do that to the best of his abilities, the now fiercely driven 'normal' boy started doing his best on everything he could, hoping to become the best big brother he could be so that his little sister could always rely on him.

As for Suguha…if she had been 'close' to Kazuto before, they were all but inseparable after the ordeal. The girl had developed both a phobia of water and an almost obsessive need to cling to her big brother at all times. With his new outlook on life and towards her, though, he happily welcomed and even embraced the change, even if it sometimes earned them some weird looks from others when the half-succubus was unable to contain her clingy affections in public. Neither of them cared, though…because they had basically been raised not to.

Midori couldn't help but smile at it all, almost unable to believe what had started as a scare that almost gave her a panic attack ended up as something so marvelous. As someone would say, despite the setbacks, all had gone according to plan.

And there was no way anything could get in the way again…

* * *

**November 15th, 2022. Kirigaya Kazuto's room, 07:15 AM…**

Mumbling nonsense as he slowly woke up, Kazuto took a deep breath and enjoyed the familiar sweet smell filling his room, before sighing in resignation at feeling two soft mounds pressed against his back and a warm body hugging his own, like always. Then, he opened his eyes and looked behind him to see the sleeping and smiling form of his little sister, her wings, horns, and tail (Which was tied around one of his legs) out in the open and not an inch of clothing covering her.

Their mom had said it was something totally normal for succubae to sleep naked, so it wasn't weird when Sugu slowly started wearing less and less clothing when it came time to get to bed. Likewise, while most 'normal people' would find weird to find their 13 and a half years old sister sleeping on their bed, for the black-haired boy it was just another constant in his life. Mom said it was a succubus thing, and perfectly normal too, so what reason did they have to doubt it? (Not that Sugu minded at all, though. In fact, lately, she had been getting even clingier, for some reason…)

Shaking his head, Kazuto reached out towards the girl's tail, untangling it from his leg and gently pulling on it, causing its owner to moan and let go of him, still half-asleep.

It said something about how used he was to this 'daily ritual' that the black-haired boy barely reacted when he turned to look at Suguha stretching out as she yawned, trying to get rid of the sleepy feeling still consuming her very well-developed body. He would have to be blind to not notice how the girl was 'growing up' waaaay faster than any girl her age should, and he had already heard the whispers and noticed the gazes of other boys, and even some girls, when they headed to school.

That wouldn't do! Nobody was allowed to look at his precious little sister like that! He would protect her from anyone that tried to have his way with her! (Of course, the fact that she was more than strong enough and had powers to easily get rid of anyone like that didn't register for him at all. Once again, not that she minded…or that she fully interpreted it as him saying that only HE could see her like this, which was something she would happily agree with).

"Sugu, wake up, we need to get ready for school."

"Hmm…I know, Onii-chan, sorry. Good morning." greeted the half-asleep demi-human while leaning forward and kissing his cheek for more time than was strictly needed, yet another routine the boy with the screwed-up upbringing saw nothing wrong with. "Last one to the shower has to wash the other's back first!"

"Hah, half-Succubus or not, you never beat me on this, Sugu!" grinned the boy as he jumped off his bed, never realizing the most likely explanation for WHY that kept happening, even as Suguha calmly floated off the beck before 'running' after him.

Bathing together in their teens was yet another thing that most people would have found odd for siblings to do, or raised their kids to know they shouldn't after a certain age…but yet again, both Kirigayas had grown up thinking it was not only normal but even encouraged by their mother. In fact, when Kazuto had mentioned a couple years back that most kids in his class said they didn't bathe with their brothers or sisters anymore, Midori had just commented such a thing was not a problem for demons at all, then asked Suguha if she had any problem with it.

She hadn't, in case it wasn't obvious, and even seemed happy to continue sharing the shower with him at every chance. And because their mother said it was okay and he wanted to be the best big brother possible, well…you can guess the rest.

Still, even as he was almost done washing his little sister's back a few minutes later, the boy found himself slowing down staring more than necessary, as he had been doing for a few months now, mentally cursing himself for doing so.

He was not blind. Kazuto knew Suguha had become an extremely attractive teenager, which was one of his main causes of worry nowadays, and the fact that she just seemed to become sexier with every year made him think he would soon to be actually beating off boys (And maybe some girls) off her with a stick, but it also made for some improper thoughts to show up on his mind every now and then, especially when they were doing something like this.

Dammit, that wasn't good! He was Sugu's big brother, the one who was supposed to always protect her and stay at her side forever! He shouldn't be looking at her with such dirty eyes!

"Onii-chan, is everything alright?" asked the half-succubus while looking over her shoulder, noticing his flushed face and his small frown.

"Yes, Sugu, don't worry…I was just thinking how pretty your wings are." casually deflected Kazuto while caressing one of the bat-like appendages, its rough texture feeling familiar and comforting under his fingers and making the girl bit her lips while looking away. "You're not having troubles flying anymore, right?"

"You know I'm not, Onii-chan…but…thanks for saying they're pretty…" mumbled Suguha while turning to smile at him…and stare a bit more intensely than usual. "Ah…"

"Well, I think we should finish up and get changed. Mom won't like if we let breakfast get cold, after all!" grinning softly, the black-haired boy ruffled his little sister's hair and headed for the shower, unaware of how she kept looking him up and down and her pupils dilated slightly for an instant, before she shook her head and followed him with a mighty blush.

Half an hour later, the siblings were finishing their breakfast and talking about seemingly normal things like an upcoming test or a project Kazuto was working in for his computer club, under the smiling gaze of their mother.

Kirigaya Midori chuckled, enjoying how happy her children were just by being in each other presence and spending time together, all thanks to the fruit of almost 14 years of carefully raising them. A plan with no few setbacks, but that their smiles proved had been more than worth it.

Especially because she could see how Suguha spent more time than needed lately staring at her adoptive brother and stuck even closer to him than before. The fact that he was still as receptive was perfect, because the girl would be turning 14 in just a few months and, as her quickly-growing body showed, puberty hit succubae like a train, even just half-ones. Her daughter would soon have a lot of 'needs' that she would take a while to learn how to control…but she would have her beloved and dearest Kazuto with her there to take care of them, with both of them being more than happy to indulge in the act.

And then, with time, both of them would grow old enough to give her lots of grandbabies! It was truly the perfect plan of a lifetime! Absolutely nothing could possibly go wrong with it!

However, as stated before…sometimes, Fate has a very twisted sense of humor…

* * *

"Ugh, dammit, it got so dark already…why did they have to take so long in fixing the machine? I just wanted to give that new game a quite look…"

Sighing with annoyance, Kirigaya Kazuto walked through the darkened streets of Kawagoe, having just gotten off a bus. Then again, given that his dear little sister was probably extremely restless at that moment waiting back at home, judging by the no less than 30 messages they had exchanged in the last 10 minutes with him reassuring her he was almost back home already, this was no surprise.

Really, all he wanted to do was go to Tokyo after school and have a quick look at a new game they were releasing in a few weeks in one of the big stores there. Suguha wanted to go with him too, like always, but she had been given a lot of homework that day and with an important exam close, she had been forced to separate for him at the bus stop while sulking all the while.

And then, as luck would have it, there had been some weird incident in the shop where apparently all electricity seemed to have failed at the same time, like something had suddenly sucked it out. As if that wasn't enough, some weird hooded girl mumbling about 'Not enough' had then rushed past him and almost send him to the floor without even apologizing. So head been forced to wait over an hour for them to restore power just to test out the game, and when he had headed back he had been forced to wait for a bus for over half an hour.

That wasn't important anymore, however. Now he was almost back home, back to Sugu, so he should concentrate on that and on getting through this strangely silent and mist-covered alleyway that…huh, that was weird. Where had all that mist come from? And…where those _bats_ flying above? He was pretty sure there shouldn't be any living anywhere near…

"Ugh…dammit, stay still! Now…aagh, why can't I do this?! Really, what's wrong with me?"

"Uh?" curious, the black-haired boy ignored both the basics of common sense (Which his 'mother' had summarily taken care of destroying for him during most of his life) and the strange tingling sensation around him to walk deeper within the alley, only to come face to face with a quite bizarre scene.

There, standing against a wall with a glassed look on his eyes, was a random high school girl, still even wearing her uniform and everything. However, it was the _other_ girl what truly drew his attention, the one that was cursing as she tried to reach out for the girl and get her face closer to her neck, only to recoil immediately and start cursing again.

Long chestnut hair and fair skin, illuminated under the moonlight under a beautiful face. Despite the dark clothes and strangely oversized…cape (?) she was wearing, she was still one of the most beautiful girls the boy had ever seen.

"I'm Yuuki Asuna! I'm from one of the proudest and most ancient vampire families that ever graced Japan! Really, how the hell can I find all theories and applications of my powers so easy after studying but I can't drain the blood of a single human?!" complained out loud the girl while grabbing her head, ignoring the enthralled high schooler in favor of banging her head against the wall. "Agh, just what kind of failure am…?!"

"Hey, you shouldn't drain the blood of a defenseless girl if she's not willing, you know?"

"…eh?"

Blinking, the chestnut-haired girl slowly stood up and turning around, her eyes widening upon seeing the single, unassuming boy that had just spoken, standing there in the middle of the Perception Barrier she had specifically set up so that nobody could come, her familiars not even getting close to him at all.

Then…she _smelled_ him. A burning, intoxicating scent like nothing she had ever felt before.

Before Kazuto's eyes, the girl's hazel eyes turned red and slitted, her skin suddenly looking unnaturally pale and pointy fangs visible in her slightly open mouth. The only reaction he gave was a curious tilt of his head.

"So…are you going to let that girl go?"

"You…smell delicious." whispered Asuna while taking a step towards him as if in a trance, her face twisting into a hungry smile.

Back in the Kirigaya Household, Kirigaya Suguha shot up from where she was worryingly waiting in her big brother's bed, all her instincts screaming at her to _find him_.

Even so, there was nothing anymore that could stop the whims of Fate. The meeting that would sink the until then relatively 'peaceful' life of the 'demonic' family into chaos had taken place.

'Normality' was about to be redefined…

* * *

**Author's Notes:** I did it, yay! This little crazy idea came about talking with a good friend a few weeks ago, and has been simmering on my mind since then. Yesterday, after finishing the Update for Lusus Naturae, I decided 'Why not?' and sat down to write it, so lo and behold, here is the prologue done! Obviously, there is a lot that it's still not shown, but the overall idea is "What if Kazuto was the only 'normal' one around?", in which the girls are all awkward 'monsters' and Kazuto is about as normal as you can expect from a boy unknowingly raised by his Succubus aunt-mom to be the mate of his Half-Succubus sister/cousin XD

As mentioned, there are no intentions of continuing this beyond this prologue, sadly, as I'm way too busy with my current fics, so I will leave it as an enjoyable one-shot :P Once again, happy Aprils Fools, everyone!


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